The present invention relates generally to integrated circuit (IC) designs, and more particularly to a sense amplifier with leakage compensation for electrical fuse cells.
Electrical fuses are often utilized in modern ICs. Typically, they are designed to blow when a current through the fuses exceeds a pre-determined threshold. When the fuses are programmed or “blown,” although not necessarily physically broken, they enter into a high impedance state. Electrical fuses are commonly used for making adjustments and repairs that are performed as late as after the chip is packaged. Since wirings are allowed at the two ends of the fuses, they can be flexibly implemented within the IC. This flexibility makes the electrical fuses desirable components for IC designs.
Conventionally, an IC includes a plurality of electrical fuse cells, each of which has at least one electrical fuse serially coupled to at least one switch device. A sense amplifier is typically implemented in the IC to detect a sensing current flowing through the selected electrical fuse cell in order to determine its logic state. The voltage level of the sensing current varies depending on the resistance of the fuse of the selected cell. The sense amplifier outputs a signal indicative of whether the fuse is blown or not, based on the voltage level of the sensing current.
During the sensing process, only one or few electrical fuse cells are selected. Ideally, the unselected electrical fuse cells should not allow an electrical current to pass thereacross. However, in reality, part of the sensing current often leaks through the unselected electrical fuse cells. This reduces the sensitivity of the sense amplifier in responding to a change of the fuse resistance. In some cases, the leakage current would cause the sense amplifier fail to detect a fuse cell that is blown.
Thus, desirable in the art of IC design is a sense amplifier with leakage current compensation features for electrical fuse cells.